1. Field of the Invention
This invention relates to the field of Automotive steering systems and more specifically to improvements in a rack bushing which is used to retain seals in the rack housing while allowing for longitudinal movement of a rack portion extending from the housing.
2. Description of the Prior Art
Typically, a bushing is provided in the rack housing or “tube” of a rack and pinion steering system to allow the rack to move longitudinally while preventing the leakage of steering fluid from inside the housing. In some cases, threaded bushings have a tendency to vibrate loose over time. While encountering a cyclical range of temperatures in which a vehicle is expected to operate, there is considerable expansion and contraction of components. When the bushing and the housing are formed of materials that have dissimilar coefficients of expansion, such as aluminum for the housing and steel for the bushing, there is opportunity for the bushing to lose its frictional engagement with the internal portions of the housing and work loose over time.
Some prior art attempts to prevent axial movement of bushings have resulted in the use of additional locking components. For instance, in US Patent Publication 2006/0219467 a non-threaded bushing is shown that contains an outer annular recess that is collocated adjacent a hole in the rack tube to which it is mounted. Material is injected through a hole into the recess to lock the bushing in place. In U.S. Pat. No. 6,644,430 a non-threaded bushing contains an annular groove on its outer surface and the tube is crushed radially inward to hold the bushing in place. In U.S. Pat. No. 6,155,375, a non-threaded bushing is shown that has an annular groove on its outer surface that is positioned below a corresponding annular groove in the rack tube. A lock wire is inserted into the grooves to hold the bushing in place.